How to handle beforeunload events while writing

If there is any input form in the window.document, I don't know if this material will help. (Search word: js confirm before leaving the form)

// Bind window.beforeunload event first
$(window).on("beforeunload", function() {
    You may lose your "return" content. Would you still like to go out?";
});
$(document).ready(function() {
    // If there's a submission event in a form,
    $("#myForm").on("submit", function (e) {
        // I'll untie the window.beforeunload binding so that it's okay to go out anytime
        $(window).off("beforeunload");
        // Submit a form
        return true;
    });
});

onbeforeunload or onclose is an event where browser support may not be available, so use onunload.

https://developer.mozilla.org/ko/docs/Web/API/WindowEventHandlers/onunload

When a user tries to move a page, it seems that he/she is trying to block the movement and print out a message.

I understand that it is impossible to block the page movement due to scripts in most browsers. I think it's probably because it can be abused on spam sites.